JP3216049B2 - Developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic developing device used for a copying machine, a printer, a facsimile, and the like, and more particularly, to a developing device suitable for forming an image with a non-magnetic one-component toner. About.

[0002]

2. Description of the Related Art A conventional developing device using a non-magnetic one-component toner is disclosed in Japanese Unexamined Patent Publication No. 62-257185. In order to form a toner supply roller, a toner supply roller made of a foamed foam is arranged to rotate in contact with the toner carrier. In this method, the toner is adhered to the surface of the toner carrier by the mechanical rotation of the toner supply roller and the electrostatic force due to frictional charging by the contact rotation between the toner supply roller and the toner carrier, and is uniformly transported.

However, with a conventional toner supply roller,
If an image with a high printing density such as solid black printing is printed immediately after an image with a low printing density such as all-white printing, the following problems occur.

First, there is a problem that the density of the front half of the solid black image is extremely higher than the density of the rear half.

Second, the latter half of the solid black image becomes non-uniform, and furthermore, there is a problem in that background fouling (hereinafter, fogging) occurs.

First, with respect to the first problem, when printing is performed at a low printing density such as all-white printing, the amount of toner movement from the toner carrier to the image carrier is reduced, so Residual toner increases. In this state, when a toner supply roller having a large foamed average cell diameter, which has been widely used in the past, is used, the residual toner on the toner carrier gradually increases because the ability to scrape the residual toner is low. Therefore, when an image having a high printing density such as black solid printing is printed next, the image density of two rounds from one week of the toner carrier becomes higher than that of the latter half.

Regarding the second problem, similarly to the first problem, when an image having a low printing density is printed, such as character printing, the toner transfer from the toner carrier to the image carrier is performed. Since the amount decreases, the amount of residual toner on the toner carrier increases.

[0008] The residual toner on the toner carrier goes to the next toner supply roller contact portion and is mixed with the new toner supplied by the toner supply roller. In this state, the residual toner is frictionally charged with the toner regulating unit and the toner supply roller several times, so that the toner charge amount increases as compared with the new toner, and the charge amount of the new toner varies. become. Therefore, when an image having a high print density such as black solid printing comes next, the residual toner having a high toner charge amount cannot move to the image carrier, and as a result, there is a problem that unevenness occurs in the image and a charging failure. A problem arises that fogging is caused by the toner.

As a countermeasure against these problems, Japanese Patent Application Laid-Open No. Sho 61-1986 discloses that a toner removing means for removing residual toner on the toner carrier is provided between the toner supply roller and the image carrier so as to contact the toner carrier. No. 43767. This is because the toner removing unit is brought into contact with the toner carrier, mechanically removes the residual toner on the toner carrier, supplies new toner with a toner supply roller, and reduces the amount of toner and the amount of charge on the toner carrier. It is to make it uniform.

However, according to this method, the positional relationship between the toner removing means and the toner supply roller as the toner supply unit is restricted, so that the toner circulation path becomes complicated, the apparatus configuration becomes complicated, and the cost increases. Cause a problem that leads to

Here, in order to clarify the difference between the present invention and the conventional example, the following conventional example will also be referred to.

Japanese Patent Application Laid-Open No. 3-41486 discloses a toner supply roller in which the diameter of a foam cell is twice or less the average particle diameter of the toner. When the toner enters the foam cells and the clogging progresses, the toner supply roller
This has the purpose of preventing the entire roller from losing elasticity and preventing the mechanical conveyance force of the toner from being reduced.

The above-mentioned prior art describes the foam cell diameter of the toner supply roller, but does not consider the problem of the ability to scrape residual toner on the toner carrier at all.

JP-A-61-28977 discloses a toner carrier having a surface roughness (Ra) of 0.1 to 0.1.
This is 5 μm. The purpose of this toner carrier is to stabilize the long-term mechanical transport force of the toner by regulating the surface roughness.

Japanese Patent Application Laid-Open No. 55-140858 discloses a toner carrier in which the height H of the peak on the surface is 1/4 to 3 times the average particle diameter of the toner, and the distance D between the peaks is the height of the peak. The irregularities are larger than H. The purpose of this toner carrier is to loosen the toner by the unevenness of the surface and the toner regulating means to form a uniform toner layer.

That is, in the above-described conventional example, the surface roughness of the toner carrier is described. However, similarly to the above-described toner supply roller, the problem of the ability to scrape residual toner on the toner carrier is discussed. No consideration is given, and no consideration is given to improving the scraping ability of residual toner in relation to the foam cell diameter of the toner supply roller and the surface roughness of the toner carrier.

[0017]

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and an object of the present invention is to always carry out stable toner conveyance and development regardless of the printing density. Another object of the present invention is to provide a developing device capable of printing an image with less fog.

Still another object is to provide an inexpensive developing device with a simple configuration.

[0019]

According to the present invention, there is provided a toner supply roller comprising a foamed foam , a toner carrier having a saw-toothed surface and rotating in contact with the supply roller. A developing device comprising:
The average cell diameter of the toner supply roller is equal to that of the toner carrier.
A surface roughness larger than the surface roughness and the toner supply roller and the toner
The peripheral speed difference is provided on the nut carrier, and the saw blade is
So that it warps and displaces in contact with the peripheral surface of the toner supply roller.
It is characterized by comprising.

[0020]

(Embodiment 1) Therefore, the details of the present invention will be described below based on an illustrated embodiment.

FIG. 1 is a block diagram of one embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes an image carrier, which is charged with a surface potential to a predetermined potential by a charger (not shown).
It is exposed by an exposure device (not shown) to form an electrostatic latent image.

Reference numeral 2 denotes a developing device using a non-magnetic one-component toner. The developing device 2 supplies a non-magnetic one-component toner to the electrostatic latent image on the image carrier 1 to visualize the electrostatic latent image. Has the following configuration.

In FIG. 1, reference numeral 3 denotes a toner hopper for storing non-magnetic one-component toner (hereinafter referred to as toner) used in this embodiment. In the toner hopper 3, a toner supply unit 4 having a function of conveying the toner from the toner hopper 3 to the developing unit is provided.

Reference numeral 5 denotes a toner regulating means for uniformly reducing the thickness of the toner layer and uniformly charging the toner. This is because the toner supply roller 7
It is located downstream of. The toner restricting means 5 has an R-shaped tip portion made of a plate material such as stainless steel, and the tip R portion is uniformly in contact with the surface of the toner carrier 6. Thereby, the thickness of the toner layer can be regulated uniformly.

Next, the toner supply roller will be described.

As the material of the toner supply roller 7, it is desirable to select a foamed foam in consideration of the polarity of frictional charging with the toner. In this embodiment, since a well-known reversal development is performed using a polyester toner having a negative polarity, a foam material having a more positive triboelectric charging polarity than this toner is required. Specifically, a polyurethane foam, a polystyrene foam, a polyethylene foam, a polyester foam, an ethylene propylene foam, a nylon foam and the like can be used. In this embodiment, a polyurethane foam was used.

The foam cell of the toner supply roller 7 is preferably a single cell. This is disclosed in JP-A-62-257185.
As disclosed in Japanese Patent Application Laid-Open No. H11-163, if the foam cells are open cells, the toner enters the inside of the foam cells of the toner supply roller 7 and eventually causes toner aggregation in the inside and the surface layer portion, thereby deteriorating toner transportability. In addition, the torque of the entire device is increased. As a countermeasure, the above-described problem can be prevented by making the foam cell of the toner supply roller 7 a single cell, preventing the toner from entering the inside from the surface layer portion, and preventing aggregation of the toner.

A hardness of 10 ° to 40 ° (measured with an Asker C hardness tester) can be used, but a hardness of 35 ° to 40 ° having a large scraping effect of residual toner is more preferable. The resistance value is 10 ³ Ωcm to 10 ⁷ Ωcm.
(Volume resistance value).

Next, the toner carrier will be described.

The toner carrier 6 is composed of a base material obtained by dispersing and molding carbon as a conductive agent in polyurethane rubber. In this embodiment, the polyurethane rubber is used as the base material. However, in order to efficiently charge the toner by friction, it is desirable that the base material be one in consideration of the polarity of the frictional charge with the toner. In this embodiment, similarly to the above-described frictional charging polarity of the toner supply roller 7, the frictional charging polarity of the base material of the toner carrier 6 needs to be more positive than that of the toner.
Therefore, in addition to polyurethane rubber, natural rubber, isoprene rubber, styrene butadiene rubber, butadiene rubber, chloroprene rubber, butyl rubber, ethylene propylene rubber,
Epichlorohydrin rubber, nitrile butadiene rubber, acrylic rubber and the like can be used.

Although the toner carrier 6 of this embodiment uses a single-layer rubber, it is well known that the upper layer of the single-layer rubber may be coated with a resin. Also in this case, it is necessary to consider the triboelectric charging polarity with the toner. As the coating material, polyethylene, polystyrene, nylon, polyurethane, polyester and the like can be used.

A hardness of 20 to 50 (measured with an Asker A hardness meter) can be used. The resistance value is 1
A material having a volume resistivity of 0 ³ Ωcm to 10 ⁸ Ωcm was used.

The toner supply roller 7 and the toner carrier 6 described above were arranged as follows.

The toner carrier 6 is, as shown in FIG.
A rubber grain on the surface of the toner carrier is disposed in a direction warped by the contact rotation with the toner supply roller, and rotates at a predetermined speed in the direction of arrow A.

If the toner particles on the surface of the toner carrier are arranged in such a direction that the rubber particles fall down, the rubber particles of the toner carrier 6 fall down by the F portion of the toner supply roller 7, and the F portion of the toner supply roller 7 The contact with the G portion of the toner carrier 6 becomes difficult. Therefore, the scraping effect is reduced, and the residual toner is G
It is left in the department.

As shown in FIG. 1, the toner supply roller 7 has a counter (in the direction C in the figure) at a contact portion B with the toner carrier 6.
The toner carrier is disposed near the outlet of the toner hopper 3 so as to rotate, and conveys the toner to the toner carrier 6.

As a result, the toner supply roller 7 in FIG.
The toner can be conveyed in the section, and the residual toner can be scraped off in E in FIG. If this direction is opposite to the direction C, the above-described pressing force and rotation speed of the toner supply roller 7 are required to obtain the scraping effect, which leads to an increase in the torque of the entire apparatus, which is not preferable.

The ratio of the peripheral speed between the toner carrier 6 and the toner supply roller 7 is 1: 0.5 to 0.9, preferably 1: 0.5.
It was set to 0.8. This is because if the peripheral speed of the toner supply roller 7 is lower than this, the transportability is deteriorated. Conversely, if the peripheral speed is further increased, the transportability is not improved so much, which leads to an increase in the torque of the apparatus. Further, the contact depth between the toner carrier 6 and the toner supply roller 7 is set to 30 μm or more, and preferably 100 μm in order to reduce the torque of the apparatus and the assembling property.
m.

In such a configuration, the average diameter of the foamed cells of the toner supply roller 7 used in the present embodiment is 50 μm to 200 μm. As described above, the average cell diameter of the foamed toner supply roller 7 is set to 50 μm.
By setting m to 200 μm, the developability of the toner can be improved and an image with less image unevenness and fog can be printed.

FIG. 2 is a graph showing the density of solid black printing immediately after all white printing. As shown in the figure, the toner supply roller having a large foaming average cell diameter of 300 μm is 100 μm or 50 μm.
It can be seen that the image density in the first half of the image is higher and the image density in the second half is lower than that of the image. This is because the foaming average cell diameter of the toner supply roller is too large with respect to the toner particle size, and thus a portion where the pressure contact state is insufficient between the toner carrier 6 and the toner supply roller 7 occurs, and the toner carrier 6
Since the residual toner cannot be sufficiently scraped off, the residual toner increases, and as a result, the image density in the first half increases.

The low image density in the second half is also due to the low scraping ability of the toner supply roller 7, as described above, so that residual toner is generated and adheres to the toner carrier 6. Rotate several times. Therefore, since the residual toner is frictionally charged several times by the toner regulating means 5 or the like, the charge amount of the residual toner excessively increases, and even if the next attempt is made to print on the electrostatic latent image on the image carrier 1, the toner carrier 6 Cannot move from above. As a result, the image becomes uneven and the density is reduced. Further, since the foaming average cell diameter of the toner supply roller 7 is large, the mechanical conveyance force of the new toner is low, and the contact with the toner carrier 6 is insufficient, so that the electrostatic force due to the triboelectric charge is reduced, and the toner This is also due to the reduced transport force.

However, when the average cell diameter of the foamed toner supply roller 7 is reduced to 100 μm or 50 μm, the ability to scrape the residual toner is improved, and further, the mechanical conveyance force and
Since the conveyance force due to the electrostatic force is also improved, the density in the first half of the image decreases and the density in the second half increases.

Hereinafter, the optimum foamed average cell diameter of the toner supply roller 7 was examined and shown.

FIG. 3 shows the relationship between the average cell diameter and the density of the foaming of the toner supply roller in the latter half of the black solid printing immediately after the all-white printing. FIG. 4 shows the foaming of the toner supply roller after printing at a printing density of about 50%. FIG. 4 is a diagram illustrating a relationship between an average cell diameter and a fog amount. First,
FIG. 3 shows that when the average cell diameter of the foamed toner supply roller 7 is about 200 μm or less, the solid black density is improved and stabilized.

It can also be seen that when the diameter of the foam cell of the toner supply roller 7 is smaller than about 50 μm, the solid black density decreases. This is presumably because the surface roughness of the toner supply roller 7 is reduced, and the mechanical toner conveying force is reduced.

The same applies to the fog amount shown in FIG. 4. When the average cell diameter of the foamed cells is 250 μm or more, a portion where the pressure contact state is insufficient between the toner carrier 6 and the toner supply roller 7 is generated. As a result, the amount of residual toner increases, and thus the charge amount of the toner becomes non-uniform, and fog occurs due to the non-uniformly charged toner.

From the above, it is understood that the average cell diameter of the foaming of the toner supply roller 7 is preferably 50 μm to 200 μm. Therefore, in this example, a foamed cell having an average cell diameter of 50 μm to 200 μm was used.

However, even when the toner supply roller 7 is used, as shown in FIGS. 2, 3 and 4, both the solid black density and the fog amount have not reached satisfactory values (allowable limit values).
This is probably because the residual toner on the toner carrier 6 has not been completely removed.

Therefore, in the present invention, the toner carrier 6 is further configured as follows.

A polyurethane rubber having a surface roughness Rmax of at least the image area of the toner carrier 6 of 2 μm to 15 μm was used.

As described above, the surface roughness R of the toner carrier 6
By setting max to 2 μm to 15 μm, the scraping performance of the residual toner is improved.

FIG. 5 is a graph showing the relationship between the surface roughness Rmax of the toner carrier and the density in the latter half of black solid printing immediately after the all-white printing. FIG. 6 shows the surface of the toner carrier after printing at a printing density of about 50%. FIG. 4 is a diagram illustrating a relationship between roughness Rmax and fog amount. First, in FIG. 5, the surface roughness Rmax of the toner carrier is about 15
If it is smaller than μm, the F portion of the toner conveying roller surely comes into contact with the G portion of the toner carrier as shown in FIG. 7B, and the residual toner can be scraped off. Therefore, it can be seen that the solid black density is improved and exceeds the allowable limit density and stabilizes.

On the other hand, Rm on the surface of the toner carrier 6
When ax is larger than 15 μm, as shown in FIG. 7A, a portion where the F portion of the toner supply roller cannot press against the G portion of the toner carrier occurs, and the residual toner on the toner carrier 6 is sufficiently scraped. As a result, the density cannot be reduced.

The Rmax of the toner carrier 6 is 2 μm.
It can be seen that the smaller the density, the lower the solid black density. This is presumably because the surface roughness Rmax of the toner carrier 6 is reduced, so that the mechanical toner conveying force is reduced.

For reference, the average cell diameter of the foamed toner supply roller 7 was set at 300 μm. according to this,
Although the tendency is similar, it can be seen that the absolute value of the solid black density is considerably reduced. This is because, as shown in FIG. 7C, when the foaming average cell diameter of the toner supply roller 7 is large, the portion where the F portion of the toner supply roller comes into contact with the toner carrier 6 is reduced, and the number of times of scraping is reduced. This is because the elastic force of the F portion is reduced due to the large foam cell diameter, and the scraping force is reduced.

Looking at the data obtained when the toner supply roller 7 has a foam cell diameter of 30 μm, the tendency is the same, but the absolute value of the solid black density is considerably reduced. This is because the foam cell diameter of the toner supply roller 7 is extremely smaller than the toner particle diameter, so that the mechanical conveyance force of the toner is insufficient, and even if Rmax on the surface of the toner carrier is changed, the solid black density is ensured. This is because toner is not supplied.

The same applies to the fog amount shown in FIG. 6, and when the Rmax of the surface of the toner carrier 6 is larger than 15 μm with respect to the foaming average cell diameter of the toner supply roller 7, as shown in FIG. , F of the toner supply roller 7
Part cannot be pressed against the G part of the toner carrier,
The toner remaining on the toner carrier 6 cannot be sufficiently scraped off, causing non-uniform charging and fogging.

In the configuration of the present embodiment, when the average particle diameter of the toner was examined by which the mechanical conveyance force of the toner supply roller 7 was effective, the average particle diameter of the toner was preferably 6 μm to 12 μm.

[0060]

As described above, according to the present invention, a toner supply roller made of a foamed foam and a surface having a sawtooth shape are provided.
A is, in the developing device comprising a toner carrier which rotates in contact with the feed roller, the toner supply roller Rights
The average cell diameter is larger than the surface roughness of the toner carrier,
Peripheral speed difference between the toner supply roller and the toner carrier
Is provided, and the saw blade is provided for the toner supply roller.
Since it is configured to warp and displace in contact with the peripheral surface ,
Immediately after printing with a low printing density such as all-white printing, even if printing with a high printing density such as solid black printing is performed, sufficient scraping performance can be achieved between the toner transport roller and toner carrier. Can be put out . Therefore , regardless of the print density, stable toner conveyance and development can be performed, and a good image free from fog can be realized with a simple structure.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a developing device of the present invention.

FIG. 2 is a diagram showing the density of solid black printing immediately after all white printing.

FIG. 3 is a graph showing the relationship between the average cell diameter of foam and the density of a toner supply roller in the latter half of black solid printing immediately after all-white printing.

FIG. 4 is a diagram showing the relationship between the average foam cell diameter of the toner supply roller and the fog amount after printing at a print density of about 50%.

FIG. 5 shows the second half of black solid printing immediately after all white printing according to the present invention.
FIG. 4 is a diagram illustrating a relationship between the surface roughness Rmax of the toner carrier and the density.

FIG. 6 is a graph showing the relationship between the surface roughness Rmax of the toner carrier and the fog amount after printing at a print density of about 50% according to the present invention.

FIG. 7 is an enlarged view of the operation of the toner carrier and the toner supply roller of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 2 Developing device 3 Toner hopper 4 Toner supply means 5 Toner regulating means 6 Toner carrier 7 Toner conveyance roller

Continued on the front page (72) Inventor Hidenori Kim 3-3-5 Yamato, Suwa City, Nagano Prefecture Inside Seiko Epson Corporation (72) Inventor Shuhei Mouri 3-5-5 Yamato, Suwa City, Nagano Prefecture Seiko Epson Shares In-company (56) References JP-A-5-224524 (JP, A) JP-A-5-181352 (JP, A) JP-A-4-55873 (JP, A) (58) Fields investigated (Int. . ^7, DB name) G03G 15/08

Claims (1)

(57) [Claims] 1. A developing device comprising : a toner supply roller made of a foamed foam; and a toner carrier having a saw-toothed surface and rotating in contact with the supply roller.
-The average cell diameter of the supply roller is the surface roughness of the toner carrier.
And the toner supply roller and the toner
The carrier has a peripheral speed difference, and the saw blade is
So that it is in contact with the peripheral surface of the
A developing device.